Proposed solution

Create a configuration schema for field types, field widget and field storage (if applicable) defined in text module.Schema in place
field.text_with_summary.settings
field.text_with_summary.instance_settings
field.text_with_summary.value
field_widget.text_textarea_with_summary.settings

Note: they are part of main field schema patch at #1953404: Add config schema to field and instance config entitiesSchema not yet in place
field.text.settings
field.text_long.settings
field.text.instance_settings
field.text_long.instance_settings
field.text.value
field.text_long.value
field_widget.text_textfield.settings
field_widget.text_textarea.settings